Bi-Deficiency Leading to High-Performance in Mg 3 (Sb,Bi) 2 -Based Thermoelectric Materials.

Mg 3 (Sb,Bi) 2 is a potential nearly-room temperature thermoelectric compound composed of earth-abundant elements. However, complex defect tuning and exceptional microstructural control are required. Prior studies have confirmed the detrimental effect of Mg vacancies in Mg 3 (Sb,Bi) 2 . This study proposes an approach to mitigating the negative scattering effect of Mg vacancies (V Mg ) by Bi deficiency, synergistically modulating the electrical and thermal transport properties to enhance the thermoelectric performance. Positron annihilation spectrometry and C s -corrected scanning transmission electron microscopy analyses indicated that the V Mg tends to coalesce due to the introduced V Bi . The defects created by Bi deficiency effectively weaken the scattering of electrons from the intrinsic V Mg and enhance phonon scattering. A peak zT of 1.82 at 773 K and high conversion efficiency of 11.3% at ∆T = 473 K are achieved in the optimized composition of Mg 3 (Sb,Bi) 2 by tuning the defect combination. This work demonstrates a feasible and effective approach to improving the performance of Mg 3 (Sb,Bi) 2 as an emerging thermoelectric material. This article is protected by copyright. All rights reserved.